Takeoff Run and Takeoff Distance

Definitions and Key Differences

Takeoff Run (TOR): This is the horizontal distance from the start of the takeoff (brake release) to a point halfway between the aircraft's lift-off (VLOF) and reaching the screen height (usually 35 ft on dry runways, 15 ft on wet runways). TOR focuses on the actual paved or prepared surface required for the aircraft to safely begin its climb.

Takeoff Distance (TOD): This is the total horizontal distance from brake release to the point where the aircraft reaches the screen height (35 ft dry, 15 ft wet), including any clearway (an unprepared area beyond the runway where the aircraft can continue to accelerate and climb but not land). TOD is always equal to or greater than TOR and is used for determining if the available runway and clearway are sufficient for a safe takeoff.

Calculation and Regulatory Considerations

• For dry runways, TOD is the greater of the actual distance to 35 ft or 115% of the all-engines distance to 35 ft, providing a safety margin.
• On wet runways, the calculation may use a 15 ft screen height due to reduced performance and increased uncertainty.
• If a clearway exists, it can only be included in TOD, not in TOR. TOR must be completed on the paved runway.
• For one-engine-inoperative scenarios, the distances are recalculated to ensure the aircraft can still safely continue or abort the takeoff.

Factors Affecting Takeoff Run and Distance

Several variables influence takeoff performance:

• Runway slope: Uphill increases required distance; downhill reduces it.
• Surface condition: Wet or contaminated runways increase both TOR and TOD.
• Runway elevation: Higher elevations reduce engine and aerodynamic performance, increasing required distances.
• Aircraft mass: Heavier aircraft need longer distances.
• Configuration: Flap settings, bleed air usage, and other configuration choices impact acceleration and climb.
• Clearway usage: Allows higher takeoff mass by extending TOD, but does not affect TOR.

Operational Implications

Pilots must always compare calculated TOR and TOD against available runway (TORA) and takeoff distance available (TODA), ensuring all regulatory and safety margins are met. Errors in V1 selection, incorrect mass/configuration data, or misjudging runway conditions can lead to inadequate takeoff performance.